At present the IPV4 public network addresses are almost exhausted, and it is predicted in the industry that they will be completely exhausted in a few years, so migration to IPV6 is inevitable. During the process of migration to the IPV6, it is crucial to ensure the intercommunication between the host and network of the IPV4 and those of the IPV6. Currently, the addressing modes of NAT (Network Address Translation) and 6 to 4 are generally adopted in the industry to solve the intercommunication between IPV4 host and IPV6 host. According to this method, address format translation is implemented depending on a gateway device between the two networks, each IPV4 address needs to be mapped to a unique IPV6 address, the IANA (Internet Assigned Numbers Authority) specially distributes an IPV6 address prefix 2002:0000::/16 to indicate that the 32 bit thereafter is an IPV4 address, and the source address and destination address of a message sent from the IPV4 network to the IPV6 network, after being added with the IPV6 prefix at the gateway, is then sent to the IPV6 network, while the prefix is deleted from the reverse message at the gateway.
The problem of the method is that the IPV6 host participating in intercommunication also must occupy an IPV4 public network address and always occupies the address during the whole process of migration from the IPV4 to the IPV6, this migration process seems to be very long at present, and since the IPV4 address space is rather rare, the number of addresses required in this intercommunication scheme cannot be supported.
In addition, this intercommunication problem does not only lie between the IPV4 and IPV6 networks, but also lie in the intercommunication between a network with novel addressing provided by IETF (Internet Engineering Task Force) and the IPV4, for example, the representatives of identity/location separation technology, LISP (Locator/Identifier Separation Protocol) and HIP (Host Identity Protocol), both define a new identifier format, which will also be regarded as an IP address with a new format by the network and host of the IPV4 when the network with novel addressing communicates with the IPV4 network, so the new network has the same problem in intercommunication with the IPV4 network as the IPV6 network.
Another problem of intercommunication lies in the support of traditional applications for a new IP (Internet Protocol) address format. During the process of migration to a new IP network, network upgrading, host operation system/protocol stack upgrading are relatively easy, but applications can hardly be synchronous with the network upgrading due to their diversity, so compatibility with the old applications is also one of the crucial problems in the period of network transition.